MI-250 Equatorial Mount

The Mountain Instrument MI-250 is a 90-100 lb capable german equatorial mount equipped with the Gemini system. Its carrying capacity actually exceeds that of the AP-900 GTO mount even though the MI-250 is about $1500-$2000 less expensive. This mount is still a bit of hidden gem in the high end mount field, although its performance is more than a good match to the AP.

Shown above is the mount as it arrived after undergoing the updgrade that includes a new base, a very nice looking white paint finish and knob-operated clutches

This is a heavy duty mount: check out this side by side image with the G11, which is no slouch itself.

Two modifications were made:

1. Base Plate adapter

My pier is a 6" column that I had ordered for the GM8 (and was compatible with the G11). Rather than tear apart the observatory floor and get an 8" pier, I decided to get an adapter plate made. See here for details. It fits quite well. I still have the option to upgrade to an 8" pier from LeSueur if need be, the bolt pattern at the base is the same as of the 6" pier.

2. Altitude adjustment smoothing

Another recent MI-250 user (May 2010) found the altitude adjustment to be very stiff when the mount is loaded and came up with a clever way to improve on it. It made sense to implement the same concept and details can be found here.

As of June 12 2010, the mount is installed and went through basic motions. Now waiting for a clear night to find out how it performs